Many aircraft, including general aviation aircraft, unmanned air vehicles (UAVs), missiles, and experimental and research aircraft, use various air data sensors and signal processing circuits to determine various flight-related parameters. For example, many aircraft include a plurality of pressure sensors to sense at least static pressure (Ps) and total (Pt) or impact pressure (Qc) during aircraft flight. The signal processing circuits, based on pressure signals supplied from the pressure sensors, determine and supply signals representative of various flight-related parameters. Such parameters may include, for example, the just-mentioned pitot or impact pressure and static pressure, as well as Mach (M), calibrated airspeed (CAS), and barometric altitude, just to name a few. In some applications, sensors and associated processing circuitry have been packaged together into what may be referred to as an air data module (ADM).
The above-mentioned flight-related data are typically derived, either directly or indirectly, from two absolute pressure measurements. These pressure measurements include static pressure (Ps) and total pressure (Pt). As is generally known, static pressure is the ambient air pressure at the present vehicle altitude, and total pressure is the sum of the static pressure and the impact pressure (Qc) due to vehicle forward velocity (e.g., Pt=Ps+Qc). For some applications, the air data pressure sensors that are used to measure static and total pressure may be subject to short, relatively high magnitude pressure pulses. For example, many missiles are stored in containers that have protective covers. These protective covers are, in many instances, blown off during missile launch sequence by, for example, various types of pyrotechnic devices. As a result, the air data pressure sensors may be exposed to a significant, and potentially damaging, pressure pulse during the missile launch sequence. This pressure pulse can be significantly higher than the operating pressure of the air data pressure sensors during flight.
The accuracy of an air data system is primarily a function of the full-scale pressure range of the associated air data pressure sensors. Pressure sensor accuracy is typically stated as a percentage of full-scale range (e.g., % f.s.r.). For example, if the full-scale pressure range of a pressure sensor is 30 p.s.i., with a specified accuracy of ±0.05% f.s.r., then the accuracy would be ±0.015 p.s.i. Thus, if an air data pressure sensor will likely be exposed to the above-mentioned overpressure condition, the air data pressure sensor should, and typically is, designed to withstand this condition, with a safety factor because the resulting pressures may be loosely controlled. As a result, air data sensors designed for a significantly higher absolute pressure range than what is needed inflight may be used to adequately withstand the overpressure condition during launch. This in turn may dictate that the air data pressure sensors have a correspondingly tighter accuracy, as a percentage of full-scale range, to achieve the desired air data measurement performance. This can significantly increase air data sensor cost, which can concomitantly increase overall air data system and aircraft costs.
In addition to the above, many unmanned air vehicles (UAVs) typically have potentially limiting size, weight, power, and cost budgets associated with the air data system. Yet, the aircraft may simultaneously have relatively stringent requirements for accuracy, wide bandwidth, and low measurement latency over a relatively wide AOA range. Moreover, there is a generally a desire that the air data system be relatively easy to install, test, and maintain.
Hence, there is a need for an air data system that is relatively small, lightweight, low cost, uses relatively low power, and is relatively easy to install, test, and maintain. There is additionally a need for an air data module and method that relatively inexpensively provides sufficient accuracy and air data measurement performance following exposure to a relatively high overpressure condition. The present invention addresses one or more of these needs.